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Aquatic Geochemistry (v.8, #2)

Strontium Isotopic Signatures of the Streams and Lakes of Taylor Valley, Southern Victoria Land, Antarctica: Chemical Weathering in a Polar Climate by W. B. Lyons; Carmen A. Nezat; Larry V. Benson; Thomas D. Bullen; Elizabeth Y. Graham; Jesicca Kidd; Kathleen A. Welch; James M. Thomas (pp. 75-95).

We have collected and analyzed a series of water samples from three closed-basin lakes (Lakes Bonney, Fryxell, and Hoare) in Taylor Valley, Antarctica, and the streams that flow into them. In all three lakes, the hypolimnetic waters have different ⁸⁷Sr/⁸⁶Sr ratios than the surface waters, with the deep water of Lakes Fryxell and Hoare being less radiogenic than the surface waters. The opposite occurs in Lake Bonney. The Lake Fryxell isotopic ratios are lower than modern-day ocean water and most of the whole-rock ratios of the surrounding geologic materials. A conceivable source of Sr to the system could be either the Cenozoic volcanic rocks that make up a small portion of the till deposited in the valley during the Last Glacial Maximum or from marble derived from the local basement rocks. The more radiogenic ratios from Lake Bonney originate from ancient salt deposits that flow into the lake from Taylor Glacier and the weathering of minerals with more radiogenic Sr isotopic ratios within the tills. The Sr isotopic data from the streams and lakes of Taylor Valley strongly support the notion documented by previous investigators that chemical weathering has been, and is currently, a major process in determining the overall aquatic chemistry of these lakes in this polar desert environment.

Geochemistry of ice-covered, meromictic Lake A in the Canadian High Arctic by John A. E. Gibson; Warwick F. Vincent; Patrick Van Hove; Claude Belzile; Xioawa Wang; Derek Muir (pp. 97-119).

The geochemical processes occurring within meromictic Lake A (maxdepth 120 m) on northern Ellesmere Island, Canada, were investigated to determinethe history of the lake and to provide a baseline for future studies. The lake contained seawaterdiluted by freshwater input that had been mixed prior to the lake's isolation from tidalaction. Input of freshwater after isolation of the lake created vertical stratification resultingin the creation of distinct oxic, suboxic and anoxic zones. Dissolved oxygen was present to 13 m,and sulphide beneath 32 m. Manganese and iron cycling dominated the redox chemistrybetween these depths. Total manganese concentrations reached 176 μM, higher thanin most other natural stratified lake or marine environments.

Keywords: arctic; biogeochemistry; meromictic; perennial ice; redox; manganese; iron

Beryllium Geochemistry in the Lesni Potok Catchment (Czech Republic), 7 Years of Systematic Study by T. Navrátil; P. Skřivan; L. Minařík; A. ŽIgová (pp. 121-133).

The biogeochemical study was carried out at the Lesni potok (LP)catchment, Central Bohemia, Czech Republic. The ecosystem was impacted by heavy acid depositionduring the industrial development in 1980–1990. The catchment is forested mostly by two tree species, Norwayspruce and European beech. The Be concentration in the granite bedrock is 12.6 mg kg^-1. Theplagioclase contains the highest Be concentrations out of the rock-forming minerals. Elevatedconcentration of Be (5.4 mu;g L^-1) in surface waters is a result of its mobilization from the soils(3.9 mg kg^-1) and weathered rock by acid precipitation. As the pH of the precipitation and consecutivelypH of the surface waters is increasing in the Czech Republic, the Be concentrations in the surface watersgradually decrease. Groundwater with high pH values contains lower concentrations of Be (0.17 μg L^-1)than surface waters. The soils at prone area of the catchment are depleted in Be compared to thesoils in the riparian zones. The vegetation located on the prone area contains lower concentrations of theBe than vegetation at riparian zones. The monitoring of Be in the environment is important with respectto its possible harmful effects on aquatic biota and root systems of the plants.

Keywords: beryllium; geochemistry; catchment; monitoring; soils; granite; surface water; groundwater; speciation

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Aquatic Geochemistry (v.8, #2)

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Aquatic Geochemistry (v.8, #2)